High Performance File System
| Developer(s) | Microsoft, IBM |
|---|---|
| Full name | High Performance File System |
| Introduced | November 1989 with OS/2 1.2 |
| Partition identifier | 0x07 (MBR) |
| Structures | |
| Directory contents | B+ tree |
| File allocation | B+ tree |
| Bad blocks | B+ tree |
| Limits | |
| Max. volume size | 64 GiB (as implemented) 2 TiB (theoretical) |
| Max. file size | 7.68 GiB |
| Max. number of files | Unlimited |
| Max. filename length | 255 characters |
| Allowed characters in filenames | Double-byte from 0x0020 to 0xFFFF |
| Features | |
| Dates recorded | Access, Creation, Modified |
| Forks | Yes |
| Attributes | Read-only, hidden, system, archive, sandwich |
| File system permissions | Yes (only in HPFS386) |
| Transparent compression | No |
| Transparent encryption | No |
| Other | |
| Supported operating systems | OS/2, Windows NT, Linux, DragonFly BSD, eComStation |
HPFS or High Performance File System is a file system created specifically for the OS/2 operating system to improve upon the limitations of the FAT file system. It was written by Gordon Letwin and others at Microsoft and added to OS/2 version 1.2, at that time still a joint undertaking of Microsoft and IBM, and released in 1988.
Among its improvements are:
HPFS also can keep 64 KiB of metadata ("extended attributes") per file.
IBM offers two kind of IFS drivers for this file system:
HPFS386's cache is limited by the amount of available memory in OS/2's system memory arena and was implemented in 32-bit assembly language. HPFS386 is a ring 0 driver (allowing direct hardware access and direct interaction with the kernel) with built-in SMB networking properties that are utilizable by various server daemons, whereas HPFS is a ring 3 driver. Thus, HPFS386 is faster than HPFS and highly optimized for server applications. It is also highly tunable by experienced administrators.
Though IBM still had rights to HPFS, their agreement with Microsoft to continue licensing the HPFS386 version is contingent upon them paying Microsoft a licensing fee for each copy sold. This was a result from the Microsoft and IBM collaboration that both IBM and Microsoft had right to use Windows and OS/2 technology. Microsoft used HPFS in Windows NT.
Due to the Microsoft dependence, limited partition size, file size limit of 2 GiB and the long disk check times after a crash, IBM ported the journaling file system JFS to OS/2 as a substitute.
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